OBD-II CODE / Misfire
P0301 · Cylinder 1 misfire detected
The computer identified cylinder 1 as the cylinder that misfired.
Part of the Misfire system guide.
Find cylinder 1 correctly
Cylinder numbering depends on the engine. Confirm the location before touching a plug, coil or injector. Compare the freeze frame and other codes with when you felt the misfire.
Separate ignition, fuel and compression
A technician can use the vehicle procedure to test spark and fuel delivery to that cylinder. If those checks pass, a mechanical test can help isolate a valve, compression or sealing problem.
When P0300 is also present
Look at which cylinders are involved and when the counts rise. A repeatable cylinder 1 miss gives a different starting point from a rough engine that logs misses across both banks.